


Rider War

by Jen425



Series: Journey Through The Decade [9]
Category: Kamen Rider - All Media Types, Kamen Rider Decade, Tokusatsu
Genre: ...of sorts, Angst, Betrayal, Complicated Relationships, Gen, M/M, Missing Scene, Multi, Rider War
Language: English
Status: Completed
Published: 2020-08-20
Updated: 2020-08-29
Packaged: 2021-03-06 20:53:52
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 2
Words: 2,256
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26005240
Author URL: https://archiveofourown.org/users/Jen425/pseuds/Jen425
Summary: He wonders if it was worth it.
Relationships: Hikari Natsumi/Kadoya Tsukasa/Kaitou Daiki/Onodera Yuusuke, Kadoya Tsukasa & A.R. Misaki Yuriko, Kadoya Tsukasa/Onodera Yuusuke
Series: Journey Through The Decade [9]
Series URL: https://archiveofourown.org/series/1782217
Comments: 11
Kudos: 20





	1. The Destroyer of Worlds

**Author's Note:**

> Decade’s ending is nonsense and I love it but here is how to forcibly make it make sense.

Everything about his power screams at him to destroy from the moment Daiki shoots him point blank in the face. It’s not an excuse, nor was his fear, but there are three cards in his pocket with clear and colored faces where all of his Kamen Ride cards had returned to their useless state… who knows when. It could have been when he entered this form, when Daiki shot him, and it could just as easily have been when Asumu and Wataru faded away. Who knows when they grew in number, for that matter.

(He remembers Yuusuke’s black eyes, Daiki’s gun inches from his face, and then… then what?

A fight. He’d killed people. He knows someone knocked him from his transformed state, at some point, since he lost his camera.

It’s vague, unclear. He… can’t remember. And that fills him with a deep seated terror.)

(Somewhere in there, he lost his camera.)

He doesn’t know, it doesn’t matter, but a voice inside him, maybe his instincts, maybe his powers, maybe even his still jumbled memories, say _kill them and things will be set right._

And he think _how do I know?_

And he doesn’t. And yet.

And yet maybe, he think, maybe he does have to do this. Be the villain. And then, from what his predecessors tell him… die.

And then maybe… maybe it could revive the others? Or something. That feels so inexplicably right. But what if he’s wrong? He’d been wrong before.

His senses are heightened even untransformed, now. It’s been a week and he’s found himself physically unable to remove his belt. Because maybe that’s all he is.

Decade. The Destroyer of Worlds.

He wonders why he made the powers in the first place.

( _“You always loved heroes_ ,” a voice whispers. And that one is a memory. It’s Daiki, an accidental meeting in some world that left Daiki just open enough to admit something.)

He wonders if it was worth it.

  
  
  


There’s a darkness behind him.

(Maybe he hates that that’s how he perceives it, with his new senses. With no denying his purpose, even as he hates it.)

Every Rider is connected to that which they fight. Tsukasa doesn’t know how he knows this, but it rings true. Tsukasa had fought the merging of worlds and Dai-Shocker, on vague words from his predecessors.

…Well.

However, this darkness is…

_Kuuga…_

“Yuusuke.”

Yuusuke is silent behind black eyes, behind a black and gold suit that strikes a different terror than one where it had been another person behind those eyes.

Even now this is still, to some extent, Yuusuke.

(A not-memory: has he seen this form before?)

_This power can kill even him…_

“I’m sorry,” Tsukasa says. Because he can’t bring himself to fully fight Yuusuke. Surely. Surely he has this power, he can give Yuusuke a choice.

(Neither of them have a choice in this battle.)

Surely fate would let him see the other’s face before one dies and the other is left with the fate of the multiverse.

_Fight him._

He supposes this is his fate.

  
  
  


He had to. He says that over and over again to himself; he had to kill that Rider he has to kill the Riders. He has to destroy everything before the web snaps back to full size.

Yuusuke’s expression, the way it hardened.

_You’ll have to kill him, too._

Tsukasa doesn’t really know how to do the right thing, even now. He’s running on instinct and adrenaline and the fact that he hadn’t been doing the right thing before so something _has_ to change.

Yuusuke is different. He’d started fighting for selfish reasons, but he was so naturally kind and good. Tsukasa could trust him.

Tsukasa has killed before this war, of course, some memories more hazy than others of Dai-Shocker and every monster he’s faced along his journey. But that was different.

Yuusuke had never looked at him like a monster except for when Tsukasa had wanted him to.

_Wouldn’t it be easier if he wasn’t begging you to stop this?_

Tsukasa rests his hands on his knees in the abandoned building he’s taken shelter in and waits until the shaking subsides.

Well, he had gotten to see Yuusuke’s face.

He commits it to memory.

  
  
  


_A ghost_.

Tsukasa rememberers once again that this is a world which shouldn’t exist, pieces pulled from everywhere and everywhen. She looks at him and the poor mooks of some merged world lay destroyed.

“Who are you?” She asks.

“Decade,” Tsukasa says. She hmms.

“I’m Tackle,” she says.

“You should leave before you get caught up in this mess,” Tsukasa says. She’s not a Rider. It feels almost strange to talk to someone he doesn’t feel the urge to kill, after two weeks of fighting.

The girl shrugs.

“I’m a part of this fight too, I think,” she says. “My partner… do you know Kamen Rider Stronger?”

Tsukasa had killed him, killed all but one with the merging of worlds nd then whichever one remained had died from the wrong end of a Rider Kick.

She’s already dead, however. Perhaps from another world?

“You should go,” he says again.

“But I’m looking for something,” Tackle argues back. “And I think you’ll help me find it.”

_A lost soul with unfinished business_ …

Tsukasa could make her stay away. He has that much power.

  
  
  


(But he’s lonely, and so is she, and maybe a part of him still wants to help, despite the futility of such an action.)

  
  
  


He considers going home, just once. Natsumi had only ever closed the door to him once, when he had chosen Dai-Shocker, because surely subjugation was better than destruction.

(A silent laugh: as if avoiding this destruction was possible.)

He doesn’t go in, because he knows. He’s always been that monster. He’s why the worlds have merged and Natsumi and Eijiro are left alone.

They would be right to turn him away, just as Yuusuke is right to fight him.

This is his fate. Nothing more than a force of destruction.

He stands across the street for what must be forever and is thankfully left unseen.

(And a small part of him wonders “why me?”)

  
  
  


(“I killed your partner,” Tsukasa says, as Tackle bandages his leg. He could do it himself. She doesn’t pause.

“I figured,” she says, and then she looks up. “But there has to be some reason why you’re fighting, right? Shigeru and I, every Rider I’ve heard of, fought because we were made by evil, but we refused to be.”

Tsukasa almost laughs, but it would come out broken and cruel, instead, he says “maybe.”

She accepts it.)

  
  
  


He doesn’t want to keep killing Riders. He wants it all to end already, but he goes through his cards and still sees all the empty ones.

(The standout, he thinks, is Skull. This new card doesn’t feel the same. A different frequency, perhaps. A different role.)

But this is his fate, isn’t it? To stand up whenever they fight. Even though Yuusuke is still using that form of darkness. That form that fills Tsukasa with an inexplicable feeling of… something.

“You okay?” Tackle asks.

Tsukasa internally shakes off his doubt.

“You should go,” he says, once again.

“Nope!”

He ignores her comment because it doesn’t matter. He’s caught Skyrider nearby, above him.

He has, at the very least, his single duty.


	2. The Ultimate Darkness

**Summary for the Chapter:**

> He thinks about the way Tsukasa had looked at him…

**Notes for the Chapter:**

> Yuuuuusukeeeeeee!!!!!
> 
> My poor baby goes through so much. I wanted to see his side of this mess just as much as Tsukasa’s, really.

Yuusuke blinks. Blinks again. Stares at Tsukasa in front of him, turned away.

The last thing he remembers is jumping in front of that attack aimed at Tsukasa. It seems his gamble played off, since they’re both here. And yet…

“Tsukasa,” he says, pulling himself to sitting. “Why am I on the ground?”

“I defeated you,” Tsukasa says. “Be grateful because I gave you your mind back, but don’t think that means I won’t or can’t kill you, next we meet.”

A wind blows, and Yuusuke shivers as he forces himself to standing.

There’s something… wrong and horrifying in the way Tsukasa speaks; it just doesn’t sound like him.

An edge that shouldn’t be there. A threat unlike what they had faced in Tsukasa’s world because there he had been smirking, aloof. This is a shattered, unflinching kind of evil to witness, and Yuusuke finds himself terrified for what he’d see in Tsukasa’s eyes.

_ Fight him _ , a voice whispers.  _ You want to fight him. He needs to die. _

“What happened to you?” He asks. “Daiki? Natsumi? Did we finally defeat Dai-Shocker?”

Tsukasa finally turns to him. His face is perfectly blank.

“I am the destroyer of worlds,” he says. “I will never be anything more or less, and I  _ will _ destroy all Riders.”

He locks eyes with Yuusuke for a long moment without blinking until Yuusuke finds himself looking away.

“I promised to fight with you,” Yuusuke says. “But I won’t let you hurt people.”

“I know.”

“Why are you doing this?”

“Because I can,” Tsukasa says, simply, and it’s said in a way where they both know that it’s not a boast but a fact. It sends another shiver through Yuusuke, which he ignores.

**Kamen Ride: D-D-D-Decade**

**Final Attack Ride: D-D-D-Decade!**

In seconds, Tsukasa stand before Yuusuke as Decade, shooting behind him, there’s the sound of an explosion and two screams.

“Stronger,” Tsukasa says. “And Chalice. I will destroy you all. I will destroy… everything.”

The most chilling part of all of this is how calmly Tsukasa says it. Every villain Yuusuke has faced with him had  _ boasted _ . Tsukasa speaks instead with his usual casual acceptance of reality, even though that reality is cold blooded murder.

It’s horrifying. The most horrifying enemy he has ever faced, and it’s  _ Tsukasa _ .

And so Yuusuke stares him down.

(He still finds himself the first to look away.)

“So be it,” he says, and he transforms in turn.

  
  
  


Yuusuke falls back, his transformation dropping, and he doesn’t bother to look up. Tsukasa doesn’t move to attack again either, however.

He wonders, does Tsukasa really want this? He hadn’t been going all out on him, and his helmet looked… wrong, Yuusuke can’t tell how. Maybe he’s being forced?

He looks up. He wants to believe in Tsukasa, he has when Tsukasa was blatantly doing selfish or horrible things, but those had been death screams behind him.

“You can stop, Tsukasa,” he says. “Right? You don’t have to destroy.”

Tsukasa is silent.

Yuusuke locks eyes with him, and this time it is Tsukasa who first looks away.

Tsukasa who runs away.

(It’s enough to know he is not being forced at all.)

  
  
  


The other Riders explain some, when they find him. That this is Decade’s fate, has always been Decade’s fate. He collapsed the worlds around an alternate Kuuga, Agito, Ryuki, Faiz, Blade, Hibiki, Kabuto, Den-O, and Kiva, as well as their allies, when he started to lose. Back when he had been leader of Dai-Shocker.

They’d found him amnesiac and tried to use him.

Yuusuke gets angry at that.

But… then he thinks about the way Tsukasa had looked at him.

For now, Decade is the bigger threat.

  
  
  


He keeps meaning to ask about Natsumi, Eijiro, Daiki, even Kivala! But he can’t make himself do it, because Tsukasa had made clear that he would kill Yuusuke, so of course he’d be willing to kill them, too.

Or maybe their deaths are why Tsukasa is like this now.

(He doesn’t fully let himself hope that they’re alive, but he does find himself imagining it, regardless. Natsumi and Eijiro are back at the photo studio. Daiki ran somewhere safe, maybe he’s even with them.)

He  _ definitely  _ doesn’t let himself search.

  
  
  


“Your alternate chose not to fight, you know,” says the alternate Faiz… Inui Takumi(?). “He used some power he was afraid of to beat back Decade, and then he left.”

“Is that why I’m still here?” Yuusuke asks. Inui shrugs.

“How could I know?” He asks. “Still, I gotta say, I couldn’t do it. If I was as close to Decade as you, and I had to fight him, I’d still see… him.”

And Yuusuke thinks about Tsukasa at home, at the photo studio, sharing a real smile with him.

And then he thinks about the blank expression on his face when he’d said he would destroy all Riders.

He shakes his head.

“I still love Tsukasa,” he says. “But the Tsukasa I knew would hate who he is now, so I’ll fight until either I stop him and save the worlds or he kills me.”

Inui huffs.

“Too many people die in our fights,” he says, and he’s looking down at his own hands. Yuusuke smiles, grimly.

“Someone has to protect people,” he says. “Even if I’m just fighting for the memory of a smile, now.”

Inui hmms, and says no more.

(Tsukasa kills him two days later.)

  
  
  


He keeps using the form. The one that comes from himself, Ultimate, that had made his alternate stop. Tsukasa avoids his attacks, doesn’t quite fight, and maybe there is something  _ of _ Tsukasa left in him, but there are other people at stake, leftover monsters terrorizing civilians in this hybrid, ever-shifting world.

He misses Tsukasa, but Tsukasa is no longer a good person, and there are other smiles at stake.

A part of him misses it, but he has to keep going.

  
  
  


Skyrider, Super-1, and the alternate Kabuto, Tendou, don’t come back from their patrol.

Five Riders, less than twenty RioTroopers.

He wonders how, wonders when, Wonders if this will ever end. 

He senses Tsukasa nearby.

_ Fight. _

The time to end this, at least, will be soon.

**Notes for the Chapter:**

> Thanks for reading!

**Author's Note:**

> Find me on Tumblr @flaim-ita or @dancingqueen-mai for just Toku edits


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